World population will likely peak at around 9.4 billion around 2070 and then decline to around 9 billion by 2100, according to new population projections from IIASA researchers, published in a new book, World Population and Human Capital in the 21st Century. Alternative scenarios included in the projections range from 7 billion to almost 13 billion by 2100. The book was officially launched today at an event at the Wilson Center in Washington DC.